Field of the invention
The present invention concerns a single front suspension arm, for supporting and steering a motorcycle wheel connected to the chassis of the motorcycle by a suspension spring directly interposed between this arm and said chassis, the said arm being adapted to turn about an axis of direction substantially orthogonal to that of the said wheel and located substantially in the median longitudinal plane of the motorcycle. The invention can furthermore, be applied, with the addition of corresponding means, to other cases, such as for example that of special vehicles provided with multiple steerable wheels in which steering the wheels can be performed wheel by wheel and where the wheel driving and steering transmission means to the wheel are located advantageously as high as possible, such as is the case especially with certain all-purpose vehicles, and light aircraft.
The suspension of a vehicle body or chassis must, in order for the vehicle to retain correct road holding, be provided independently for each wheel, but this requirement results in connections between the wheel and the suspension and steering means being complex. The suspension of fourwheeled vehicles has been greatly simplified by the type of suspension known as "Mac Pherson suspension" and described for example in French patent No. 1 156 145. In the case where this type of suspension is applied to a steerable wheel, the wheel stub axle is rotatively mounted on a support arm that is connected to a shock-absorber tube connected by a link to the central portion of the chassis and the body of the vehicle rests, in a relatively high rest position, directly upon a helical spring which is thus located abutted by its upper end against a rest plate integral with the body and by its lower end against a rest shoulder integral with the shock-absorber tube or forming part of this latter.
This compact and economical suspension solution has been widely adopted in the manufacture of automobiles but until now it has never been used for vehicles having a single front steerable wheel as motorcycles since these latter require a front wheel bearing perfectly centered in the plane of symmetry of the wheel.
The prior art contributed certain solutions to this problem by proposing for the front wheel of the motorcycle a Mac Pherson type suspension where the single wheel is carried by a single arm forming the support leg and connected to a suspension arm through a ball and socket-pivot connection centered upon the steering axle of the front wheel.
In order to obtain the connection between the handle bar and the front wheel, it has been proposed to use high and low links, pivotally connected to one another, and rotatably mounted respectively, for the higher one in a steering part moved by the handle bar and the lower link on the single arm parallel to the wheel stub axle and according to an axis substantially perpendicular to the steering axis. This type of pivoting links connection between the handle bar and the single wheel arm operates correctly and allows precise steering but has proved to be too bulky, with respect to the scissor-like movement of the links that requires, in closed scissor position, a large amount of space towards the front.
The present invention concerns a particularly advantageous novel solution from the point of view of bulkiness (thus adapted to be covered in a very aerodynamic manner) and from the point of view of reliability in all the movement situations of the telescopic unit, to the problem consisting of guiding a single arm carrying a wheel stub axle and motorcycle front steerable wheel, the said single arm being directly connected to the chassis through a suspension spring and by one (or several) suspension arm(s).
Another object of the invention is to apply the steering means of the main object to vehicles other than a front steerable wheel motorcycle, in which the steering control mechanism is not performed by means of a handle bar but for example by means of suitable control means, these means being mechanical, hydraulic, electric, pneumatic or other, thus allowing to control the steering of a single arm carrying a steerable wheel, stub axle or wheel axle, without requiring to provide a bulky rigging around the median portion and if possible also around the upper part of the said suspensionsteering block. Such a solution can be applied for example among others to special vehicles in which is not necessarily sought an identical steering at any moment of two wheels of a pair of left and right wheels, such as has been the case up to now with classical motor vehicles.
According to the invention, a coupling device is proposed between a vehicle steerable wheel and a steering control member, the steerable wheel being carried by a single arm connected to a suspension arm mounted rotatably on a transverse axle of the vehicle body and, at one of its ends, at its other end, mounted pivotally on the transverse arm by a swivel and ball joint, the pivoting center of which is located in the alignment of the rotation axis of the steering arm and a suspension and/or shock-absorber block, for example with telescopic cylinder and movable rod, being interposed between an upper rest end of the single arm and a rest piece mounted fixedly on the chassis of the vehicle or forming part thereof, wherein the single arm comprises a transmission and guiding rod directed upwards and eccentrically and rigidly fixed thereupon and this rod cooperates with a sliding bar, upon which is pivotally connected at one end at least one link the other end of which is pivotally connected to a steering ring connected to the steering control member.
The transmission and guiding rod can be disposed over its whole length at a distance substantially constant from the axis of rotation, of the single arm, i.e. is substantially parallel to that axis, or it can be inclined with respect to the axis of rotation of the single arm in order to substantially match the surface of a cone during the rotation of the single arm about its axis.
According to another embodiment of the invention, the transmission and guiding rod is hollow and is provided with an outer surface hardened by any appropriate means and rolling sliding means, for example ball bearings, roller bearings, needle bearings, are interposed between the sliding bar or piece and the transmission and steering rod.
The sliding piece and/or at least the outer surface of the transmission and steering rod are preferably made of a material producing low friction and the transmission and guiding rod presents a cylindrical outer surface.
According to another embodiment improving the guiding of the slide bar on the rod, at least two parallel crowns of bearing members, for example, balls, rollers, needles, are interposed between the slide bar and the transmission and the transmission and guiding rod.
According to a further embodiment, the link is constituted by two distinct links linked to each other by a C-shaped part in order to form a single-piece assembly, these two distinct links being pivotally connected by their lower end on the slide bar that surrounds at least one rolling member interposed between the transmission rod and the slide bar ring.
In order to avoid the degradation of the transmission and guiding rod by projections during shell integral with the coupling support carrying the said transmission rod and integral with the single arm.